Project title: Practical demonstration of scheduling techniques for flowering patio plants
Project number: PC 203
Project leader: Dr Steve Adams
Report: Final report, October 2004
Key workers: Warwick HRI:
Dr S. Adams – Project leader
Dr V. Valdes – Project manager
Miss G. Woodward – Project assistant
Mr J. Horridge – Project assistant
HRI Efford:
Dr Ian Clarke – Initiated the project
Location: Warwick HRI, Wellesbourne, Warwick, CV35 9EF
Project co-ordinator: Mr A. Spires - Young Plants Ltd, Church Lane, Alveston, Stratford upon Avon, Warwickshire, CV37 7QJ
Start date: 1 August 2003
Completion date: 31 July 2004
Key words: Flowering, scheduling, temperature, daylength, photoperiod, supplementary lighting, Antirrhinum, Argyranthemum, Bacopa, Bidens, Diascia, Felicia, Fuchsia, Lobelia, Lotus, Nemesia, Petunia, Sanvitalia, Scaevola, Verbena.
Whilst reports issued under the auspices of the HDC are prepared to the best available information, neither the authors nor the HDC can accept any responsibility for inaccuracy or liability for loss, damage or injury from application of any of the concepts or procedures discussed.
The contents of this publication are strictly private to HDC members. No part of this publication may be copied or reproduced in any form or by any means without prior written permission of the Horticultural Development Council.
© 2004 Horticultural Development Council
Contents
Page number
1. Grower Summary 2
1.1. Headline 2
1.2. Background and expected deliverables 2
1.3. Summary of the project and main conclusions 3
1.4. Financial benefits 9
1.5. Action points for growers 10
2. Science section 11
2.1. Introduction 11
2.2. Materials and methods 12
2.3. Results and discussion 14
Antirrhinum LuminaireTM Deep Purple 17
Antirrhinum LuminaireTM Harvest Red 19
Argyranthemum Sultans Dream 21
Bacopa Snowflake 23
Bidens aurea 25
Diascia Joyce’s Choice 27
Felicia Blue 29
Fuchsia Alice Hoffmann 31
Fuchsia Barbara Windsor 33
Fuchsia Betty 35
Fuchsia Dark Eyes 37
Fuchsia Deep Purple 39
Fuchsia Gene 41
Fuchsia Liza 43
Fuchsia Lyle's Unique 45
Fuchsia Marcia 47
Fuchsia Maybe Baby 49
Fuchsia Nice ‘n’ Easy 51
Fuchsia Patio Princess 53
Fuchsia Pink Marshmallow 55
Fuchsia Pink Spangles 57
Lobelia Richardii 59
Lobelia White Star 61
Lotus Bertholetii 63
Nemesia Blue Lagoon 65
Petunia Surfinia Blue 67
Sanvitalia Aztec Gold 69
Scaevola Brilliant 71
Verbena New Ophelia 73
Verbena Red Knight 75
2.4. Conclusions and general discussion 77
3. References 82
Appendix 1 – Experimental plan 83
Appendix 2 – Pictures showing the ‘visible bud’ stages 84
Grower summary
1.1. Headline
-
The project demonstrated how a simple screening protocol could be used to investigate how temperature, daylength and supplementary lighting affect flowering in a range of patio plants.
-
Warmer temperatures hastened flowering in all of the patio plant species/cultivars studied, with the exception of Lotus. Long days promoted flowering in 24 out of the 30 cultivars examined, while supplementary lighting hastened flowering in around half of the cultivars tested.
1.2. Background and expected deliverables
Patio plants have become an increasing part of the bedding and pot plant industry for spring and summer sales. They are often vegetatively propagated and ideally the finished product is sold in flower. Many plants use daylength as a signal for floral induction. However, daylength alone is an ambiguous signal in spring and autumn and, hence, some plants use a combination of photoperiod and chilling to ensure that they flower in spring and not in autumn. Furthermore, temperature usually affects flowering time even in species that do not require chilling. There also is evidence to suggest that for a number of species the time to flowering can be hastened by increased light levels.
This work set out to demonstrate a screening protocol that could be used by growers on their own nurseries to quantify the way in which different species/cultivars respond to their environment, as well as providing valuable information on the responses of 30 different cultivars (14 species). The trial was designed to address the following questions:
-
Does temperature influence the speed of flowering?
-
Do plants develop flowers faster under long/short days?
-
Is flowering improved by the use of supplementary lighting?
1.3. Summary of the project and main conclusions
Patio plants (30 cultivars of 14 different species; Table 1) were obtained as rooted cuttings from commercial propagators. Plants arrived from week 2 to week 5 of 2004. Cuttings were potted up into 9cm pots on arrival at Warwick HRI and placed into a range of different environmental treatments within 4 different glasshouse compartments/blocks.
Experimental Plan
Block 1 Block 2 Block 3 Block 4
SD LD SD LD 5oC 5oC 15oC 15oC
Plants were inspected three times a week so that dates of visible bud appearance and flower opening could be recorded for each plant. The plant height, or in the case of trailing species the length of the longest shoot, was recorded for each plant when 50% of the plants of a given treatment had flowered.
Temperature
Plants were grown in four identical glasshouse compartments each 41m2. Two compartments were set to provide a heating temperature of 5oC, and the other two were set to 15oC. Vent temperatures were set to 3°C above these heating set-points. The 15°C compartments initially ran slightly above this set-point and temperatures were fairly stable, while the 5°C compartment fluctuated more with changes in ambient temperature. The difference between the 5 and 15°C compartments diminished over the course of the experiment as the ambient temperatures increased over time.
Warmer temperatures hastened flowering in 13 out of the 14 species examined (29 out of the 30 cultivars examined) (Table 2). Low temperatures only promoted flowering in Lotus. In nearly all of the cultivars studied warmer temperatures hastened both the appearance of visible buds (Table 1) and the rate of flower development. Therefore, warmer temperatures could be used to hasten flowering of a wide range of patio plants. In most plants this also increased plant growth, although for some may have resulted in a slight loss of compactness. Growth regulators were not used in this trial, and may be used to elevate this problem.
Daylength
At each temperature, one compartment initially provided natural short days (SD), although the daylength increased over the course of the experiment. The other compartment received day-extension lighting (LD) provided by tungsten bulbs (~1.7 µmol/m2/s at bench height (~ 100 lux)) so as to give a minimum daylength of 15 hours (lit from sunset to 23:00 h (GMT)), although this also increased over the course of the experiment due to an earlier sunrise. To avoid problems associated with light pollution in the SD compartments, blackout screens were used on the walls of each compartment from sunset until sunrise.
Most of the species/cultivars were shown to be long day plants (Tables 1 and 2). The only plant in which flowering was hastened by short days was Lotus, while Argyranthemum, Bidens, Diascia, Felicia, and Verbena ‘Red Knight’ showed no significant response to daylength. The response to long day lighting was very pronounced in some species. For example, flowering was hastened by up to 40 days in Petunia (Surfinia). Therefore, there is considerable potential to use day extension or night break lighting to promote flowering, although crops grown slightly later in the year, when daylengths are increasing, may benefit less from this treatment. The fact that very few patio plants are short day plants means that lighting could be used on a combination of species to hasten flowering and make flowering time more predictable. The effect of daylength was often on reducing the time to visible bud; flower development was generally less sensitive to daylength. Therefore, long day lighting would not need to be applied over the whole life of the crop and could be applied for only a limited duration.
A detrimental effect of long day lighting was increased stem elongation (Table 3). If tungsten lamps were used commercially this might result in increased use of growth regulators. However, the increased stem elongation was most likely a result of the red:far-red ratio of the tungsten lamps and not a response to long days per see. Therefore, it would be worth considering the use of other lamp types, for example, compact fluorescent lamps which have a different spectral output.
Light integral (supplementary lighting)
W
Figure 1. Photograph showing the layout of plants and lamps.
ithin each compartment, half of the plants received supplementary lighting, which was provided by two 400W SON/T lamps per compartment. At plant height supplementary light levels were on average 41µmol/m2/s (~3000 lux). SON/T lamps were baffled so that the unlit treatment in the same compartment was unaffected. The supplementary lighting was on for 8 hours per day from 08:00 - 16:00 h (GMT). Natural light levels increased over the course of the experiment and so supplementary lighting gave a proportionally larger effect early in the year when the quantity of natural light was low.
The response to supplementary lighting tended to be less pronounced compared with the effects of temperature and daylength. Supplementary lighting hastened flowering in around half of cultivars studied (Table 2). However, the maximum response was one week. Therefore, the potential for manipulation of flowering through supplementary lighting is limited unless they are used to create long days. The benefits would be greater for early crops. However, the costs of applying supplementary lighting are much greater than the use of low intensity long day lighting using compact fluorescent or tungsten bulbs. Although supplementary lighting may have an added benefit of increasing plant quality as a result of enhanced growth.
Table 1. The effect of temperature, daylength and supplementary lighting on reducing the number of days to visible bud of a range of patio plants. For example, Antirrhinum ‘Deep Purple’ had visible buds 28 day sooner in the 15°C set-point compartments when compared with the 5°C compartments.
Cultivar
|
Reduction in the time to visible bud (days)
|
Temperature
|
Daylength
|
Light integral
|
5°C
|
15°C
|
SD
|
LD
|
-SON/T
|
+SON/T
|
Antirrhinum Lum. Deep Purple
|
|
28
|
|
131
|
|
5
|
Antirrhinum Lum. Harvest Red
|
|
22
|
|
10
|
|
|
Argyranthemum Sultans Dream
|
|
9
|
|
|
|
5
|
Bacopa Snowflake
|
|
|
|
|
|
|
Bidens aurea
|
|
7
|
|
|
|
|
Diascia Joyce’s Choice
|
|
25
|
|
|
|
7
|
Felicia Blue
|
|
|
|
|
|
4
|
Fuchsia Alice Hoffmann
|
|
373
|
|
171
|
|
|
Fuchsia Barbara Windsor
|
|
253
|
|
201
|
|
3
|
Fuchsia Betty
|
|
13
|
|
101,5
|
|
3
|
Fuchsia Dark Eyes
|
|
32
|
|
301,5
|
|
|
Fuchsia Deep Purple
|
|
29
|
|
245
|
|
|
Fuchsia Gene
|
|
25
|
|
12
|
|
3
|
Fuchsia Liza
|
|
27
|
|
245
|
|
|
Fuchsia Lyle's Unique
|
|
155
|
|
195
|
|
3
|
Fuchsia Marcia
|
|
22
|
|
5
|
|
|
Fuchsia Maybe Baby
|
|
13
|
|
131,5
|
|
|
Fuchsia Nice ‘n’ Easy
|
|
283
|
|
121
|
|
5
|
Fuchsia Patio Princess
|
|
21
|
|
15
|
|
46
|
Fuchsia Pink Marshmallow
|
|
243
|
|
211
|
|
|
Fuchsia Pink Spangles
|
|
293
|
|
201
|
|
2
|
Lobelia Richardii
|
|
93
|
|
271
|
|
|
Lobelia White Star
|
|
16
|
|
22
|
|
|
Lotus Bertholetii
|
See text
|
|
See text
|
|
|
See text
|
Nemesia Blue Lagoon
|
|
9
|
|
|
|
6
|
Petunia Surfinia Blue
|
|
273
|
|
461
|
|
|
Sanvitalia Aztec Gold
|
|
354
|
|
142
|
|
|
Scaevola Brilliant
|
|
19
|
|
>10
|
|
7
|
Verbena New Ophelia
|
|
19
|
|
10
|
|
3
|
Verbena Red Knight
|
|
8
|
|
|
|
8
|
1 Difference reduced if temperature reduced 4 Difference reduced if LD
2 Difference reduced if temperature increased 5 Difference reduced if pinched
3 Difference reduced if SD 6 Difference reduced if in larger plug
Table 2. The effect of temperature, daylength and supplementary lighting on reducing the number of days to flower opening of a range of patio plants. For example, Antirrhinum ‘Deep Purple’ had open flowers 30 day sooner in the 15°C set-point compartments when compared with the 5°C compartments.
Cultivar
|
Reduction in the time to open flowers (days)
|
Temperature
|
Daylength
|
Light integral
|
5°C
|
15°C
|
SD
|
LD
|
-SON/T
|
+SON/T
|
Antirrhinum Lum. Deep Purple
|
|
30
|
|
131
|
|
4
|
Antirrhinum Lum. Harvest Red
|
|
27
|
|
8
|
|
|
Argyranthemum Sultans Dream
|
|
16
|
|
|
|
|
Bacopa Snowflake
|
|
27
|
|
4
|
|
4
|
Bidens aurea
|
|
18
|
|
|
|
|
Diascia Joyce’s Choice
|
|
28
|
|
|
|
6
|
Felicia Blue
|
|
10
|
|
|
|
5
|
Fuchsia Alice Hoffmann
|
|
383
|
|
161
|
|
|
Fuchsia Barbara Windsor
|
|
293
|
|
211
|
|
4
|
Fuchsia Betty
|
|
20
|
|
111,5
|
|
|
Fuchsia Dark Eyes
|
|
37
|
|
291,5
|
|
|
Fuchsia Deep Purple
|
|
30
|
|
185
|
|
|
Fuchsia Gene
|
|
31
|
|
11
|
|
4
|
Fuchsia Liza
|
|
33
|
|
255
|
|
3
|
Fuchsia Lyle's Unique
|
|
205
|
|
155
|
|
3
|
Fuchsia Marcia
|
|
29
|
|
|
|
|
Fuchsia Maybe Baby
|
|
225
|
|
121,5
|
|
|
Fuchsia Nice ‘n’ Easy
|
|
333
|
|
121
|
|
5
|
Fuchsia Patio Princess
|
|
306
|
|
121
|
|
|
Fuchsia Pink Marshmallow
|
|
23
|
|
211
|
|
|
Fuchsia Pink Spangles
|
|
313
|
|
211
|
|
2
|
Lobelia Richardii
|
|
273
|
|
281
|
|
|
Lobelia White Star
|
|
263
|
|
201
|
|
2
|
Lotus Bertholetii
|
See text
|
|
See text
|
|
|
See text
|
Nemesia Blue Lagoon
|
|
22
|
|
2
|
|
6
|
Petunia Surfinia Blue
|
|
363
|
|
401
|
|
|
Sanvitalia Aztec Gold
|
|
384
|
|
122
|
|
3
|
Scaevola Brilliant
|
|
443
|
|
141
|
|
5
|
Verbena New Ophelia
|
|
28
|
|
13
|
|
|
Verbena Red Knight
|
|
8
|
|
|
|
7
|
1 Difference reduced if temperature reduced 4 Difference reduced if LD
2 Difference reduced if temperature increased 3 Difference reduced if SD
5 Difference reduced if pinched 6 Difference reduced if in larger plug
|